The present invention relates generally to a zoom optical system and electronics incorporating the same, and more particularly to a compact zoom optical system and electronics incorporating the same. The electronics used herein, for instance, include digital cameras, digital video units, personal computers, mobile computers, cellular phones and personal digital assistants.
In recent years, personal digital assistants acronymed as PDAs and cellular phones have seen an astonishing explosion. Some such systems with built-in compact digital cameras or digital video units, too, have grown. For such digital cameras or digital video units, CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) sensors are now used as image pickup devices. In such digital cameras or the like, image pickup devices each with a receptor plane having a relatively small effective area are used. Accordingly, when the digital cameras or the like are made compact, a sensible tradeoff must be offered between size reductions and cost reductions while the performance of their optical systems is kept high. So far, a zoom optical system of the −+−+ construction has been available as one of slimmed-down, low-cost optical systems.